As it is commonly understood, hands free answer capability enables a telephone subscriber to answer an incoming call without physical manipulation of the telephone set. Thus, answering is accomplished simply by speaking a reply. The spoken work is then "picked-up" by an activated microphone and the answer is transmittted back to the calling party. Such a feature is finding acceptance in key telephone systems for use on the intercom link. U.S. Pat. No. 3,743,791 issued July 3, 1973 to Duff-Simon is directed to such a feature, which is implemented in a single link intercom. Some key telephone systems, however, are large enough to support a mutilink intercom where concurrent communication connections may be established between several telephone stations. Under such a situation an incoming call can arrive at a telephone station on any one of a number of links.
This poses a problem in that, without hands free answer capability the subscriber would push the key associated with the activated calling intercom link. This key operation would serve to connect the transmitting and receiving network with the selected calling intercom link. With hands free answer capability it is precisely this manual operation which is eliminated. Thus, it is desirable to arrange such a system so that at the calling station the calling intercom link is automatically selected and the microphone activated and connected to the proper intercom link, all without manual involvement on the part of the subscriber.
A further object of the invention is to arrange such a hands free answer feature in a manner that, notwithstanding the fact that the switchhook or pickup keys at the called station remain unactivated by the subscriber, only one call at a time may be completed to a called station.
A still further object of the invention is to control such a hands free answer feature in a manner to allow multilink intercom operation using as much common equipment as possible and arranged in a manner so that stations equipped with hands free answer capability are entirely compatible with stations not so equipped and such that station users may, from time to time, elect to bypass the hands free answer feature.